For a number of years, a portable heavy duty tapping apparatus and system has been available which used a hydraulic motor to drive a lead screw tapping tool. One such prior tapping unit was the subject of U.S. Pat. No. 4,050,835, issued to Robert C. Womack. This unit functioned well, however, it required the inclusion of a splined spindle interconnecting between the hydraulic motor and the lead screw. The slidable spline spindle permitted the hydraulic motor to be rigidly mounted and allowed the lead screw and attached tapping tool to move into and out of the work piece, according to lineation caused by rotation of the lead screw. The inclusion of the spindle with the slidable hydraulic spline caused the unit to be elongated, required maintaining an overlapping interconnecting coupling between the spline shaft from the motor and the spline sleeve of the lead screw. Although the units functioned well and continued to function in many applications, a more compact, lighter weight and shorter tapping unit is sometimes needed, both for additional portability and also for reducing clearance required for tapping certain types of holes where exterior clearance (as with partially assembled machinery) was not available for the elongated hydraulic tapping tool which was available. In instances of large diameter tapping, the stroke of the machine was less than the length of the lead screw threads so that adequate overlapping of the splines was maintained to withstand the torque.
An object of this invention is to provide improved tapping apparatus for heavy duty tapping operations, which includes a compact lightweight tool unit with integrally attached hydraulic motor, which motor slides in the tool unit for short coupled movement with the tapping lead screw, the tool unit being powered from a remote hydraulic power unit.
Another object of this invention is to provide such apparatus which is compact and designed for ready portability and for ready set up at a job site location.
A further object of this invention is to provide such apparatus where the hydraulic motor is a low speed, high torque motor with internal gearing, for direct drive of the tool unit tapping lead screw without an interposed spindle.
Still another object of this invention is to provide such apparatus, including a heavy duty high torque tapping tool unit with a sliding motor, which is simple in construction and economic to manufacture.
A still further object of this invention is to provide such apparatus including a tool unit with a lead screw feed of the tap, and which is designed to prevent more than minimal damage to the tool unit in the event of control failure.
Another object of this invention is to provide such apparatus including a short coupled lightweight tool unit capable of tapping holes up to two inches in diameter.
A further object of this invention is to provide such apparatus including a tool unit adapted for use with a multiple tap head.
Still another object of this invention is to provide such apparatus including a lead screw tool unit designed for ready changeability of the lead screw and lead nut assembly for adapting the tool for use with taps of different leads.
It is another object to provide a durable lead screw tapping tool unit which has a stroke or depth of tapping capability which is substantially equal to the length of threads on the lead screw.
It is also an object to provide a lead screw tapping unit in which the lead screw itself provides an internal bore into which a motor drive shaft is coupled and also in internal receptacle into which the tapping tool is accepted so that minimum coupling length and tool length is achieved.